The present invention relates to a rear wheel holding mechanism of the center bolt-type for a motorcycle having a cantilever swing arm rear wheel suspension and, more specifically, to a rear wheel holding mechanism facilitating mounting of the rear wheel to the motorcycle suspension.
Japanese Patent Provisional Publication (Kokai) No. 59-77911 discloses a rear wheel mounting mechanism for mounting a rear wheel on a cantilever swing arm. This rear wheel mounting mechanism has a rear axle having a radially extending flange provided with a plurality of stud bolts, and a rear wheel fastened to the flange by screwing nuts on the stud bolts. Japanese Patent Provisional Publication (Kokai) No. 61-129386, on the other hand, discloses a rear wheel mounting mechanism of a so-called center bolt type in which an axle having one end provided with an external thread extends coaxially through the hub of the rear wheel and a single axle nut is screwed onto the threaded end of the axle to fasten the rear wheel thereto.
The first-identified rear wheel mounting mechanism having a plurality of stud bolts requires excessive work for fastening or unfastening the plurality of nuts in mounting the rear wheel to, or in removing it from, the rear wheel mounting mechanism. The second-identified rear wheel mounting mechanism, being of the center bolt type, requires less work in fastening or unfastening a single nut for mounting the rear wheel to, or in removing it from, the rear wheel mounting mechanism. However, since the rear axle of the latter rear wheel mounting mechanism has a comparatively large diameter and is provided with an external thread, the outside diameter of the external thread is inevitably large, and, hence, a large torque is required to be applied to the axle nut in fastening the rear wheel to the rear axle. Accordingly, these known rear wheel mounting mechanisms are subject to further improvement in order to further facilitate replacement of the rear wheel for carrying out maintenance work. For racing motorcycles, in particular, facilitation of the rear wheel replacement is a significant subject.
Accordingly, it is an object of the present invention to provide a rear wheel holding mechanism of a center bolt type capable of fastening the rear wheel of a motorcycle, or the like, to its rear axle by screwing a single axle nut on the rear axle requiring a comparatively small torque to, thereby, improve the working facility.